1. Field of the Invention
The present invention generally relates to keyboards used for inputting operations of computer apparatuses. More specifically, the present invention relates to a keyboard having a light emitting function which can be operated even under dark environments.
2. Description of the Related Art
Conventionally, keyboards which can be operated even in dark environments have been developed.
A keyboard using EL (electroluminescence) elements is suggested in, for example, Japanese Laid-Open Patent Application Publication No. 2002-251937. In this keyboard, a character, a mark, or the like is printed on an upper surface of a key top. An elastic member and a link mechanism are provided at a lower part of the key top. A reinforcing plate and a membrane sheet having a contact point are provided under the elastic member and the link mechanism.
Light is irradiated from a rear side of the key top by the EL element provided at a lower part of the membrane sheet. The light is irradiated from the rear side of the key top so that the character, mark, or the like printed on the upper surface of the key top is brightly luminous. As a result of this, the character, the mark, or the like printed on the upper surface of the key top can be visually recognized even in a dark environment.
Keyboards having LEDs (light emitting diodes) and light guide plates are suggested in, for example, Japanese Laid-Open Patent Application Publication No. 6-22017 and Japanese Laid-open Patent Application Publication No. 2007-280810. While a lighting operating life of the EL element is approximately 3000 hours which is relatively short, it is possible to continuously use the LED for a long time. In these keyboards, characters or the like printed on the key tops are luminous.
However, in the keyboard suggested in Japanese Laid-Open Patent Application Publication No. 2002-251937, in addition to their being a problem of the lighting operating life of the EL element, an area is required where a driving electric source is arranged because a high voltage is used. Accordingly, the keyboard may be large so that the keyboard may be heavy.
Furthermore, in the keyboards described in Japanese Laid-Open Patent Application Publication No. 6-22017 and Japanese Laid-Open Patent Application Publication No. 2007-280810, light emitted by the corresponding LEDs is incident on side surfaces facing each other of the light guide plate. Accordingly, in order to obtain even and sufficient luminance, it is necessary to provide two boards or the like where the LEDs are arranged, left and right or up and down. Therefore, the keyboard may be large so that the keyboard may be heavy.
It is desirable that a key board used for the notebook type computer apparatus be as small as possible.